Dungeons
Normal dungeons are fine, it does get tedious to travel to them; thankfully this is going to get resolved soon™. The monster density within some dungeons is pretty bad. Also, it seems like every single dungeon has ghosts in it as a filler enemy, instead of having more enemies that fit the theme of the dungeon.
Some ranged monsters are a little too aggressive in their micro, making it incredibly tedious to catch a group of ranged attackers who keep backing away and spreading out.
Why is there no experience reward for completing a normal dungeon? This is a downgrade to D3 rifts, where at least the rift guardian dropped nice items and you were granted a rewarding amount of experience for the completion. Normal dungeons have no completion reward of any kind.
Nightmares
Does anyone else find these modifiers to be nothing but annoying? Potion breaker, slow, cold enchanted elites, resource burn, and so many other modifiers that I and many others salvage because playing them is just ridiculous. The modifiers need to be fun, not annoying. Burning my limited resource isn’t fun, not for me and not for anyone.
The reward for completing nightmares needs to be increased, both in terms of items and experience. Vendors sell better items than the ones given as a reward, it’s just draining to run them. It was more fun when I had glyph experience to look forward to, but without that, nightmares are just a more annoying version of regular dungeons.
Nightmares slow you down enough to make running through normal dungeons as fast as you can yield equal or greater experience per hour, especially with profoundly cancerous modifiers like slow. There are only a couple of tolerable modifiers.
Additionally, sigil drops seem kind of weird, I continuously receive sigils of the same 3-4 dungeons. There is no variety in sigil drops. Not only do I keep getting the same dungeon, but also the same modifiers. I had 5 blind burrows drop all with the slow and drifting shade modifier. I went to craft new ones, 3/9 were blind burrows. Of the 115 dungeons that exist on the map, it seems odd that I continue to receive the same ones.
Conclusion
All of that combined just makes nightmares an overall awful and draining experience. For as simple as the linear design of D3 rifts and GRs were, they were far more fun to do and it felt continuously rewarding to kill the rift guardian and get the completion experience at the end than the dungeons.